Competitive Relationships between Parula Warblers and Other Species during the Breeding Season

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Abstract
The foraging of Parula Warblers (Parula americana) and potential competitors (wood warblers and kinglets) was studied in spruce forests in Maine and oak-gum forests in Louisiana. While no other species foraged in spruces in a manner nearly identical to the Parula Warbler, their overall usage of spruces was high, and may have been an important factor restricting Parula Warblers to edges of the forests. No other species in Louisiana foraged heavily in crowns of trees comparably to Parula Warblers, and Parula Warblers foraged widely through the crowns. Gene flow from large southern populations may prevent more complete adaptation to spruce forests, but an already-heavy usage of this habitat by other species severely restricts opportunities for such an adaptation.